#include<bits/stdc++.h>

using namespace std;
using ll = unsigned long long int;
using lc = complex<double>;

int main(void) {
    constexpr ll MOD = 1e9 + 7;
    constexpr double PI = acos(-1);
    cout << fixed << setprecision(32);
    cin.tie(0); ios::sync_with_stdio(false);

    double p;
    cin >> p;
    // E = p(1+E)
    // p/1-p
    cout << p/(1-p) << endl;
}